Drying apparatus



DRYING APPARATUS Filed Jan. 26, 1943 5 Sheets-Shget 1 xxxxxxxxxx 5 Sheets-Sheet 2 F. M. MCBETH DRYING APPARATUS Filed Jan. 26, 1945 March 5, 1946.

March 5; 19 46.

DRYING APPARATUS Filed Jan. 26, 1943 5 Sheets-Sheet 3 F. M. MCBETH 2,395,933

Mar-c115, 1946.

F. M. M C BETH DRYING APPARATUS Fiied Jan. 26, 1943 s Sheets-She t 4 March 5, 1946.

F. M. M BETH DRYING APPARATUS Filed Jan. 26, 1943 5 Sheets-Sheet 5 FREEMAN/'7. NcBE M Patented Mar. 5,1946

OFFICE DRYING APPARATUS Freeman M. McBeth, Harrisburg, Pa. Application January 26, 1943, Serial No. 473,637

7 Claims.

The present invention relates to improvements in drying apparatus, and more particularly to apparatus for drying or dehydrating slices of potatoes, carrots, beets and other vegetables or fruits, although not restricted to this use.

An important object of the present invention is the provision of an apparatus of this'character which will effectively dry material passing therethrough without adversely afiecting the material.

Another object of the invention is to provide an apparatus of this character in which the de- In the drawings, wherein for the purpose of illustration is shown a preferred embodiment of the invention, the numeral I designates the discharge end of a blancher or other treating device sired rate of drying may be obtained, and maintained by automatic control mechanism.

A furtherobjeot of the invention is to provide an apparatus of the above mentioned character in which the temperature, humidity content and direction of the current of drying medium may be effectively controlled.

Still another object of the invention is the provision of means in an apparatus of this character for directing the drying medium into intimate contact with all of the material being treated.

Other objects and advantages of the invention will be apparent during the course of the following description.

In the accompanying drawings, which form a part 'of this specification, and wherein like numerals denote like parts throughout,

Figure 1 is a longitudinal elevation of an apparatus embodying the invention, parts being broken away.

Figure 2 is a top plan view thereof, partsbeing broken away.

Figure 3 is a longitudinal sectional view of the conveyor for delivering material to the drier, parts being broken away.

Figure 4a is a longitudinal sectional view of the inlet end of the drying apparatus, parts being broken away.

Figure 4b is a similar view of the outlet end of the apparatus, showing the portion of the drying apparatus broken away at the right-hand side of Figure 4a.

Figure 5 is a fragmentary longitudinal sectional view of the delivery end of one of the drying conveyors.

Figure 6 is a diagrammatic view of the drying apparatus illustrating the flow of drying medium therethrough and the method of controlling the temperature and humidity content thereof, and,

Figure 7 is a detail elevation of a portion of the apparatus, illustrating the means for placing tension upon the conveyor belts, parts being broken away.

" diameter of the sprockets. blanching device I0 is deposited on the upper run from which the potato slices or other material.

are discharged in a condition requiring drying. The material to be dried is discharged onto the upper run of a continuous conveyor ll extending upwardly at an angle of about 30 to a point above the inlet end of the main drying casing. The conveyor II is disposed within a canopy l2 which completely encloses the conveyor and is shaped to provide a large chamber l3 above the conveyor. A blower casing l4 opens into the chamber l3 adjacent the inlet end of the conveyor and a motor driven blower i5 is mounted within the blower casing to force air under pressure into said chamber Ill. The blower l5 may be supported in a suitable spider l6 carried by the blower casing to firmly support the blower while permitting the free passage'of air. A suitable air heater I1 is disposed in the discharge end of the blower casing l4 and may be of any suitable constructiomsuch as a radiator formed of steam heated coils, permitting the passage of air from the blower l5 to the chamber l3. Air filter cloths l8 are preferably disposed at both sides of the heater I1, as shown in Figure 3.

The runs of conveyor l I pass around sprockets l9, one of which isdriven, and the conveyor runs are spaced apart a distance determined by the Material from the of the conveyor II and carried up the length of the conveyor to the inlet end of the main drying casing. A short, curved or bent bafile plate 20 is disposedin a longitudinal position adjacent the upper run of the conveyor II in the space between the two runs of the conveyor and adjacent the lower end thereof. A second somewhat longer baffle plate 2! is disposed adjacent the underside of the upper conveyor run and about midway between the ends of the conveyor. A long 'bafile plate 22 underlies the plates 20 and 2|, being spaced therefrom, and stopping short of the ends of the conveyor. The conveyor runs are of perforate material, such as mesh screen, and are supported between the sprockets by means of spaced transverse slats 23 so as to maintain a spaced relation with the baflle plates 20, 2| and 22 disposed between the conveyor runs. Air currents passing through the upper run of the conveyor, and impinging against the short plate 20 will be deflected sharply to pass through the conveyor run intothe chamber 13. Currents of air which strike the plate 2i willbe deflected less sharply but will be turned back to pass through the conveyor run, as shown by the arrows in Figure 3. Air currents which pass between the plates 7 2| and 22 and impinge against the latter will be deflected upwardly through the conveyor run adjacent the upper end thereof. Thus it will be seen that the disposition of the baflle plates between the conveyor runs insures contact between the hot air currents from blower l and the material on the upper run of conveyor H.

In order to direct'the currents of air through the-conveyorand against the baflle plates therebetween, a pair of normally adjustable baflle plates 24 are pivotally mounted at their centers within the chamber 13 and between the blower l5 and convey& H. The bailles 24 may be independently adlusted to direct the blower onto any desired portion of the conveyor and into contact with the plates 20, 2i and 22 between the conveyor runs.

An adjustable baille plate 25 is pivoted at one end adjacent the top of the conveyor ll within the canopy to deflect air onto the upper end of the conveyor.

A vent pipe 26 extends upwardly from the top of canopy l2, communicating with th interior thereof. A pivoted damper 21' is disposed within the vent pipe 25 to control the passage of air therethrough. A humidostat or wet bulb 28 is disposed in the top of the canopy l2 and is operatively connected to a damper controlling mechanism 29. The control mechanism 23 determines the position of damper 21 and is in turn controlled by the humidostat 2B. When the damper isc losed, all of the air from canopy l2 passes into the main drier. When the damper 21 is in any of its open positions, part of the air passes through the vent and out of the apparatus while the remainder of the air passes into the main drier. The proportion of the air vented will be determined by the position of the damper .valve which will be controlled by the control mechanism 29 and humidostat 2B.

The main drying mechanism is enclosed in an enlongated rectangular casing 30 mounted upon suitable legs or supports 3|. The casing 30 is divided longitudinally into three compartments by means of an upper partition 32 and a lower partition 33. Each compartment is provided ,with three longitudinal conveyors 34, the ends of which are spaced 2. short distance from the ends of the casing 30, as shown in Figure 6. The conveyors are alternately staggered so that the receiving end of each conveyor underlies the discharge end of the conveyor next above it. Ob-

viously, the conveyors are therefore required to move alternately in opposite directions. The first conveyor 34 of the upper compartment underlies the discharge end of the conveyor H and receives material therefrom and moves in a direction toward the right as viewed in Figure 6. The conveyor immediately therebelow will move toward the left so as to discharge material onto the receiving end of the last conveyor of the compartment which is moving toward the right. The conveyors of th other two compartments traverse similar paths, and it will thus be seen that the product is moved in alternate directions through varying stages of temperatures, as will be understood as the description proceeds. Openings are provided in the partitions 32 and 33 to permit passage of the material from one compartment to the next lower compartment. The conveyors 34 are mounted upon sprockets 35 at each end of the casing 33, and the sprockets 33 at the inlet end or the casing 33 aredriven by suitable motors 33 through chains or gears 31 "to move the conveyors in the desired direction;

currents of air from the The motors 33 are of a variable speed type so that the speed of the respectiv conveyors may be varied to regulate the travel of the material through the various compartments and to compensate for shrinkage of the material as the drying progresses. A similar motor 38 drives the upper sprocket of the conveyor l I.

The upper partition- 32 is provided with an opening 39 disposed beneath the discharge end of the lowermost conveyor of the upper compartment to permit passage of material from the upper compartment to'the middle compartment, as shown in Figure 41). A depending wall is disposed at the right-hand edge of the opening in Figure 4b and is inclined towards the inlet end of the casing sothat air passing from right to left of Figure 4b in the middle compartment.

will pass the opening 33 without entering it. Side walls 4| are disposed on the sides of opening 33 and cooperate with the inclined wall 40 to form a chute below opening 39. A sliding, manually adjustable plate 42 is mounted on the partition 32 with a down curved lip 43 extending into opening 39 and adapted to be adjusted to control the effective length of opening 39.

A similar opening 44 is provided in the opposite end of partition 33 and has its wall 45 inclined in th opposite direction from wall 40 to permit passage of air from left to right in the lower compartment without entering opening 44. A sliding plate 43 controls the size of opening 44, and is of the same construction as plate 42.

The conveyors 34 may be of any suitable construction. but are preferably of mesh material to permit the free passage of air. Suitable supporting surfaces 41 are provided beneath each run of the conveyors to support the conveyor runs and prevent sagging thereof. Transversely disposed angle irons 43 are provided to take the weight of the surfaces 41. Y

A main air vent 49 extends upwardly from the top of the discharge end of casing 30 and is providedv with adamper valve 50. The damper 50 is regulated automatically by a control mechanism 5| which is operated by a humidostat or wet bulb 52 disposed in the top of the .upper compartment of the main casing at the discharge end thereof.

It will be seen that the material deposited upon the upper conveyor 34 will travel alternately from left to right and from right to left until it reaches the lowest conveyor, the discharge end of which extends out through the casing to overlie a suitable receptacle 53 into which the dried material is dropped, as illustrated in Figure 4b. The material will rest upon the mesh runs of the conveyors and be subjected to the passage of heated air as it travels through the casing. If the material is in the form of slices or the like, it will be inverted as it drops from one conveyor to the next. The surfaces .41 will support the conveyor runs in the desired position. If desired, a tensioning mechanism may be employed to-maintain the conveyor runs in a taut condition. Such a mechanism is illustrated in Figures 1 and 7. The conveyor sprocket shafts at the discharge end of the casing 30 are mounted in crossheads 54 which slide in longitudinal guideways 65. A longitudinal guide rod 56 is connected to each crosshead and extends freely through an opening in a stationary vertical abutment 51. A coil middle conveyor ofthe lo er compartment underlies the opening 44 and erminates a substantial distance therebeyond to conduct air from blower 68 past the opening 44. Three adjustable baflles 62 are disposed within the conduit 59 to direct the air in the desired direction. A main air inlet conduit 63 is connected to the intake of the blower. An air filter 64 is disposed in the conduit 63adjacent the inlet end thereof,

and an air heater 65, which may be of the steam coil radiator type, is disposed between the filter and blower. A control mechanism 66 regulates the heater 65 and is in turn controlled by a dry bulb thermometer 61 arranged in the inlet end of the lower compartment.

Air from blower-68 passes from left to right through the lower compartment and into conduit 68 at the opposite end thereof. A heating unit 69 is arranged in conduit 68 between the casing 38 and a blower lo to raise the temperature of the air from the lower compartment. A variable speed pulley 1| operates blower .10 while a conduit 12 connects the outlet of the blower 18 to the middle compartment. A baflle wall 13 underlies opening 39 to pass air from conduit 12 past the opening 39. Three adjustable baflies 74 are disposed in conduit 12 adjacent the casing 38 to direct the air in the desired direction.

A dry bulb thermometer I is arranged in the inlet end of the middle compartment and regulates the control mechanism 16 which controls the heating unit 69. Air from conduit 12 passes from right to left through the middle compartment. An outlet conduit 1'! will receive some of the air from the middle compartment, the balance of the air passing through the opening 44 into the lower compartment to mix with fresh air from conduit, 59. communication between the middle'compartment and the conduit 11, and its position is regulated by a control mechanism 19 which in turn is regulated by a humidostat or wet bulb 88. The position of the valve 18 determines the proportion of air which will pass through the conduit 11.

The conduit I1 discharges into the inlet end of an air conduit 8| between an air filter 82 and a heating unit 83 to be mixed with fresh air passing therethrough. Ablower 84 draws air through the conduit 8| and discharges it through a conduit 85 into the inlet end of the upper compartment' of the casing 38 to be mixed with air from canopy l2 and passed through the upper com partment from left to right. Two adjustable deflecting baiiies 86 are disposed in the conduit 85 to guide the air to the various conveyors in the upper compartment. A bafiie wall 89- underlies the opening between the canopy I2 and casing- 30 to conduct air from the conduit 85 past the opening. The heating unit 83 is regulated by a control mechanism 8'! which in turn is con- I trolled by a dry bulb thermometer 88 arranged at the outlet or right-hand end of the upper compartment. The air from the upper compartment will pass through vent 49 to be exhausted-or through opening 39 to be mixed with air from conduit 12, or will be divided, part going through vent 49 and part through opening 39; depending upon the position of valve 50, which in turn is dependent upon the moisture content of the air.

Suitable pivoted baifles 89 are disposed at spaced intervals over, between and under the runs of the conveyors 34. These 'bailles or deflectors may be mounted upon the angle irons 4'8 and are positioned to pass the air. currents back and forth through the mesh runs of the conveyors to bring the air into intimate contact with the'material thereon.

The heated air entering the lower compartment will drop in temperature as it approaches the outlet end of the compartment, but its temperature will be raised by heater 69 before it is passed into the middle compartment. Its temperature will again drop as it passes through the middle compartment, but heater 83 will raise the temperature of the air before passing it into the upper compartment.

The-thermometers and heater regulators will control these temperatures as desired, while the humidostat and valve control mechanisms will control the air currents to maintain the desired moisture content.

In dehydrating many substances there is a tendency to case harden the same. In other words, if a constant high temperature is employed and maintained throughout the drying treatment, a crust or film is produced upon the surfaces of the material, with the result that a certain moishood of 130 degrees when itpasses into the con- A pivoted valve 18 controls' ture content is sealed Within the material. Such a condition is avoided inthe present invention by what may be termed a progressive intermittent increase in temperature and control of the moisture content within the dryingchamber. For instance, air currents forced into the conduit 59 have a temperature of approximately degrees which obviouslywill be reduced by contact with the material to a temperature in the neighborduit 68. At this point, however, the air passes through the heater unit 69 raising the temperature thereof to approximately degrees for discharge into conduit 12 and into the middle compartment of the drier. Again the air will become cooled during its passage through the material and as it discharges into the air duct 11 will be at a temperature of approximately l40 degrees. The final heating of the air is by way of the heating unit 83 which is so controlled as to heat the air to a temperature of approximately degrees for passage through the upper compartment of the drier unit, the air as it leaves the latter compartment'by way of the vent 49 or opening 39 having a temperature of approximately 160 degrees. It will be notedthat there is a variance of about 20 degrees in the several stages and that the high temperature of air in the middle compartment is the same as the low temperature in the upper compartment, and for the purpose of economy, the'air from the upper compartment maybe passed into the middle compartment by virtue of the opening 39. The amount of air which may be reverted back to the middle compartment may be controlled by setting of the valve 50 in the vent 49. i

The above temperatures are purely exemplary,

and variances therefrom may be effected through 'proper setting of the. thermometers and heat regulators.

While I have shown and specifically described a preferred form of the invention, this is by way 75\of illustration only, and I consider as my own,

4- aseaess 'drying chamber having superimposed compartments, each compartment having an opening provlding communication with the compartment next above, the openings being positioned at opposite ends of the respective compartments, conveyor means within each compartment, the lowermost ofwhich is adapted to discharge material into respective openings in the partitions, means for feeding material in-a preheated state to the uppermost compartmen means for forcing heated air successively throughsaid compartments, means for progressively increasing the temperature of the heated air in its passage from the lowermost to the uppermost compartment, means for venting a portion of the air from the uppermost compartment, and means for diverting a portion of the air from the uppermost compartment to an intermediate compartment for recirculation therethroug 2. The structure of claim 1 in which temperature controls are provided for the heated air and said vent means is provided with a humidostat controlled valve to determine the proportion of air returned for recirculation.

3. A dehydrating apparatus comprising a main drying chamber having horizontally disposed partitions dividing said chamber into three superimposed compartments, each of said partitions having an opening providing communication between adjacent compartments, a plurality of conveyors in each compartment arranged to pass material from one conveyor to the conveyor next below and through the openings in said partitions, means for forcing heated air into the lower compartment adjacent one end of the drying chamber, means for removing the heated air from the lowercompartment adjacent the opposite end of the drying chamber and discharging it into the middle compartment adjacent said opposite end of the drying chamber, a heater for reheating said air before discharge into the middle compartment, means adjacent said one end of the drying chamber for dividing said heated air passing through the middle compartment and diverting a portion of said air to the lower compartment for admission with the heated air forced into the lower compartment, means for receiving the remaining portion of the heated air from the middle compartment, meansfor mixing fresh air therewith, a heater for increasing the temperature of the air mixture, means for discharging the heated air mixture into the upper compartment adjacent said one end of the drying chamber, and means adjacent said opposite end of the drying chamber for venting a portion of the heated air from the upper compartment, the remaining portion, of the heated air passing to the middle compartment through the opening in the partition between the upper and middle compartments.

4. The structure of claim 3 in which the heaters are provided with temperature controls and some of said compartments are provided with humidity controlled valves to determine the proportion of air to return for recirculation through some of the compatments.

5. A dehydrating apparatus comprising a main drying chamber having means for conducting material through varying stages of heated air, an endless perforate conveyor operatively associated with said drying chamber for feeding material thereinto, a canopy housing said conveyor,

g means for forcing heated air into said canopy in a direction longitudinally of the conveyor, adjustable air deflecting means within the canopy operative to control, air from the forcing means, and air deflecting plates positioned between the runs of the conveyor and extending in a direction substantially longitudinally of the conveyor, said air deflecting plates being arranged in spaced staggered overlapping relation to form an air passageway between the runs of the conveyor and the forward ends of the plates being curved upwardly in the direction of the upper run of the conveyor.

6. A dehydrating apparatus comprising a, main drying chamber having partitions dividing said chamber into separate compartments, each of said partitions having an opening forming communication between adjacent compartments, a plurality of conveyors in each compartment, the conveyor next adjacent each partition depositing material through the opening therein onto the upper conveyor in the next adjacent compart- 'ment, adjustable means associated with each forcing heated air successively through said compartments at increased temperatures, means for controlling the temperature of the air in each compartment, means for controlling the moisture content of the heated air in each compartment, and a wall depending from each partition and associated with the opening therein, said wall being inclined downwardly in the direction of air passage through the compartment below the partition and extending beneath a portion of the opening to prevent upward passage of air therethrough.

'7. A dehydrating apparatus comprising a main drying chamber having partitions dividing said chamber into separate compartments, each of said partitions having an openingrforming communication between adjacent compartments, a plurality of conveyors in each compartment, the conveyor next adjacent each partition depositing material through the opening therein onto the upper conveyor in the next adjacent compartment, adjustable means associated with each opening for varying the size thereof, means for forcing heated air successively through saidcompartments at increased temperatures, means for controlling the temperature of the air in each compartment, means for controlling the moisture content of the heated air in each compartment, and a bafiie wall beneath the conveyor receiving material from the opening thereabove and underlying said opening.

FREEMAN M. McBE'I'H. 

